JPH0517991B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a piston pin, and more particularly to a piston pin constructed of a light metal composite reinforced with reinforcing fibers.

Prior Art Conventional piston pins for internal combustion engines are made of steel, which is relatively heavy, making it difficult to reduce the weight and increase the output of internal combustion engines. Attempts have been made to construct piston pins from light metals such as aluminum alloys compositely reinforced with fibers, but such piston pins have poor sliding characteristics on their cylindrical outer circumferential surfaces, and the piston pin itself or Since the pin hole wall surface of the connecting rod and the pin boss wall surface of the piston, which are mating members, are subject to increased wear, a cylindrical body made of a light metal reinforced with reinforcing fibers or a metal sleeve is fitted on the outside of the cylindrical body. Attempts have been made to coat the cylindrical outer circumferential surface of a metal sleeve with a hard metal (Japanese Patent Application Laid-Open No. 131859/1983,
Utility Model No. 56-132347).

However, in such conventional piston pins, the reinforcing fibers are generally oriented in one direction along the axis of the piston pin or at 0° to the axis of the piston pin.
It is oriented by winding a prepreg sheet containing reinforcing fibers in a cylindrical shape around the axis of the piston pin, and depending on the orientation of the reinforcing fibers, the rigidity and thermal expansion of the piston pin are sufficient. Since this is not controlled, problems such as separation of the fiber-reinforced metal part and the metal sleeve and cracking of the metal sleeve occur due to differences in deformation modes between the fiber-reinforced metal part and the metal sleeve. For this reason, countermeasures such as dividing the metal sleeve into three parts have been proposed (Japanese Unexamined Patent Application Publication No. 1983-1999).
131859), but such piston pins are expensive and require a metal sleeve and fiber-reinforced metal part to completely avoid the problems of delamination and cracking caused by long-term thermal cycling and stress loads. It is impossible to achieve sufficient adhesion.

Purpose of the Invention In view of the above-mentioned problems with conventional piston pins having a structure in which a metal sleeve is fitted on the outside of a fiber-reinforced metal part, the inventors of the present invention have developed a piston pin that is helically oriented at various pitch angles. A metal sleeve is fitted onto the outside of a cylindrical body made of a light metal composite reinforced with reinforced fibers, and the cylindrical outer peripheral surface of the metal sleeve is coated with various hard metals to manufacture piston pins. As a result of tests and the like, it has been found that the various problems described above in conventional piston pins can be solved by setting the pitch angle within a specific range.

The purpose of the present invention is to compare a piston pin made of fiber-reinforced metal, which is lightweight, relatively inexpensive, and has excellent durability, and such a piston pin, based on the knowledge obtained as a result of experimental research conducted by the inventors of the present invention. It is an object of the present invention to provide a method that can be manufactured at low cost and with high productivity.

Structure of the Invention According to the present invention, the invention is made of a light metal composite reinforced with reinforcing fibers helically oriented around the axis at a pitch angle of ±65° to ±70°. a cylindrical intermediate layer made of metal and extending along the axis around the core; and an outer layer of hard metal that covers the cylindrical outer peripheral surface of the intermediate layer. A fiber molded body made of reinforcing fibers spirally oriented at a pitch angle of ±65° to ±70° is formed around the piston pin and the axis, and the fiber molded body is placed inside a metal sleeve. After preheating, the mold is placed in a mold, a molten light metal is poured into the mold, the molten metal is solidified while being pressurized, a portion consisting essentially only of the light metal is removed from the resulting solidified body, and the This is achieved by a piston pin manufacturing method in which the cylindrical outer peripheral surface of a metal sleeve is coated with a hard metal.

Effects and Effects of the Invention According to the piston pin according to the present invention, the light metal constituting the core of the piston pin has a pitch angle of ±65° to
Compositely reinforced with reinforcing fibers spirally oriented at ±70°, the rigidity and thermal expansion coefficient of the core, especially the radial thermal expansion coefficient, and the rigidity and thermal expansion coefficient of the metal sleeve are substantially the same. This prevents the core and metal sleeve from peeling off, and also prevents bending stress acting on the entire piston pin, compressive stress acting on the piston and the part inserted through the connecting rod, and preventing the piston from peeling off. It is possible to obtain a lightweight and relatively inexpensive piston pin that has the strength and durability to withstand shear stress acting on the portion between the inserted portion and the connecting rod inserted portion.

Further, according to the piston pin manufacturing method of the present invention, a fiber molded body made of reinforcing fibers oriented helically at a predetermined pitch angle is placed in a metal sleeve, and a composite of reinforcing fibers and a light metal is formed. Because the reinforcing fibers are fused to a light metal, the orientation and volume ratio of the reinforcing fibers are maintained at predetermined values even during the process of compositing the reinforcing fibers with the light metal. A piston pin having a helically oriented core can be efficiently and inexpensively manufactured using a method in which the fiber molded body is placed in a metal sleeve and preheated, and the molten light metal is pressurized. This not only ensures that the molten light metal penetrates between the individual reinforcing fibers of the fiber molded article, but also ensures good adhesion between the reinforcing fibers and the light metal. The metal constituting the metal sleeve and the matrix metal of the core undergo an alloying reaction, and as a result, a piston pin with excellent adhesion between the core and the metal sleeve can be manufactured at low cost and efficiently.

In addition, the light metal in the piston pin and the manufacturing method thereof according to the present invention may be an aluminum alloy, magnesium, or an alloy containing these as main components.
The reinforcing fibers are carbon fibers, alumina fibers,
It may be silicon carbide fiber, alumina-silica fiber, boron fiber, etc., and the volume percentage of the reinforcing fiber depends on the type of reinforcing fiber or light metal, the fiber diameter of the reinforcing fiber, etc.
It is preferable to set it to 50-70%. Further, the metal constituting the intermediate layer may be any metal that reacts with the light metal as the matrix metal constituting the core, but is particularly preferably steel such as stainless steel, and the hard metal constituting the outer layer is It may be a single metal such as molybdenum or chromium, an alloy such as stellite, or a composite metal material such as nickel in which particles of silicon carbide are dispersed. The cylindrical outer circumferential surface of the layer may be coated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Embodiment 1 FIG. 1 is a partially cutaway illustrative perspective view showing one embodiment of a piston pin according to the present invention. In the figure, 1 is an aluminum alloy composite reinforced with carbon fibers 3 (Torayca (registered trademark) M40 manufactured by Toray Industries, Inc.) oriented spirally around the axis 2 at a pitch angle of ±67.5°. 4 (JIS standard AC7A) and has a hollow hole 5 extending along the axis 2. A cylindrical intermediate layer 6 made of stainless steel (JIS standard SUS304) and extending along the axis 2 around the core 1 is provided integrally with the core 1 on the outside of the core 1 . middle layer 6
The cylindrical outer peripheral surface of is covered with a coating layer 7 of molybdenum.

The piston pin constructed as described above was manufactured as follows according to the manufacturing method of the present invention.

First, stainless steel (JIS
Carbon fiber 3 around the pipe 8 made of standard SUS304)
By winding strands (6000 single yarns) of Torayka (registered trademark) M40 manufactured by Toray Industries, Inc. (manufactured by Toray Industries, Inc., with a single yarn diameter of 7 μm) using filament winding, a cylindrical layer with a pitch angle θ = 67.5° is formed. cylindrical layers with an angle θ = -67.5° are laminated alternately in the radial direction, with an outer diameter of 21 mm as shown in Fig. 2;
A cylindrical fiber molded body 9 with a length of 1500 mm was formed.
After cutting this fiber molded body 9 into a length of 85 mm, as shown in FIG.
By inserting it into the center of a pipe 10 made of stainless steel (JIS standard SUS304) with a length of 105 mm, a cylindrical body 11 consisting of the fiber molded body 9' and the pipe 10 with a length of 85 mm was formed.

Next, although not shown in the figure, the cylindrical body 11 is
After preheating to 750℃, as shown in Figure 4,
placed in a mold 12 for high-pressure casting;
Pour molten metal 13 of aluminum alloy (JIS standard AC7A) at 740°C, and pour the molten metal with plunger 14.
A pressure of 1500 Kg/cm ² was applied, and the pressurized state was maintained until the molten metal 13 was completely solidified. Molten metal 13
After the solidified body is completely solidified, the solidified body is taken out from the mold 12 using the knock-out pin 15, and a cylindrical body is taken out by removing the part consisting essentially only of aluminum alloy from the solidified body by machining. The pipe 8 and the aluminum alloy solidified inside the pipe were removed by massaging the body with a drill, and the cylindrical outer peripheral surface of the pipe 10 was removed.
By grinding about 0.5mm and cutting both ends, the outer diameter is 21.95mm as shown in Figure 5.
A cylindrical piston pin rough material with an inner diameter of 8 mm and a length of 75 mm was obtained. The pipe 1 of the cylindrical body 16 thus obtained
The cylindrical outer circumferential surface of 0 was coated with molybdenum by plasma spraying, and the coating layer was finally polished to form an outer diameter of 22 mm as shown in Fig. 1.
The piston pin has an inner diameter of 8 mm and a length of 75 mm. The volume percentage of carbon fiber in this piston pin is 65%.
The thickness of the outer layer of molybdenum was approximately 30 μm.

Also, for the purpose of comparison, carbon fiber has a pitch angle θ=±
The same procedure and same conditions as Example 1 above with the same dimensions except that the spiral orientation was 45°, ±55°, ±60°, ±65°, ±70°, ±75°. manufactured piston pins.

These piston pins are used to connect the piston 18 and the connecting rod 19 as shown in FIG. Pressing, load when load P is 3 tons,
That is, the actual operating load and the point A at that time, that is, the intermediate part between the part inserted into the piston and the part inserted into the connecting rod, where it is empirically known that the largest deformation occurs. measuring the deformation strain in the direction parallel to the axis 2 of the piston pin at the position of the outer peripheral surface on the side of the piston head 18a,
A compression test was also conducted in which the load P was increased to measure the load at which the piston pin would break, that is, the breaking load. The results of this compression test are shown in FIG.

From this figure 7, each pitch θ of carbon fiber is ±
It can be seen that when the angle is between 65° and ±70°, the breaking load of the piston pin becomes maximum, and the deformation strain at point A is maintained at a small value.

Furthermore, when the piston pin manufactured in the above-mentioned Example 1 was assembled into a 4-cylinder 2000cc gasoline engine and a durability test was conducted for 200 hours at an engine speed of 5200 rpm and a full load, it was found that the piston pin manufactured in the above-mentioned Example 1 was No harmful deformation, peeling of the interface between the core and intermediate layer, or cracking of the intermediate layer was observed in the piston pin manufactured in this process, and this piston pin has sufficient strength and durability. It was recognized that the Furthermore, when the piston pin manufactured in Example 1 was cut and the interface between the intermediate layer and the core was observed using an optical microscope, it was found that the intermediate layer was It was confirmed that there is an alloy layer formed by melting and mixing the constituent stainless steel and the aluminum alloy as the matrix metal of the core, and that the intermediate layer and the core are in strong contact with each other. It was done.

Furthermore, for comparison purposes, layers oriented cylindrically unidirectionally along the axis of the piston pin and layers oriented cylindrically circumferentially around the axis of the piston pin are stacked radially alternatingly. A prototype piston pin was manufactured in the same manner and under the same conditions as in Example 1 above, except that the core was made of aluminum alloy compositely reinforced with carbon fiber. When this was subjected to a durability test conducted under the same conditions as the durability test described above, it was found that 5.
It was observed that cracks had occurred at the interface between the intermediate layer and the core after a period of time had passed. After the test, the radial coefficient of thermal expansion of the core of both piston pins was measured, and the coefficient of thermal expansion of the core of Example 1 was 12.5.
×10 ^-6 and was found to be substantially the same as the radial coefficient of thermal expansion of the intermediate layer, whereas the coefficient of thermal expansion of the core of the piston pin in the comparative example was substantially the same as that of the intermediate layer. The coefficient of thermal expansion in the radial direction was 0, which was significantly different from the coefficient of thermal expansion in the radial direction of the intermediate layer, and it is presumed that this was a factor in the occurrence of cracks and peeling.

The weight of the piston pin manufactured as described above is
At 86g, this piston pin was 28% lighter than a conventional forged steel piston pin.

Embodiment 2 FIG. 9 is a partially cutaway illustrative perspective view showing another embodiment of the piston pin according to the present invention. In the figure, 21 is a magnesium alloy composite reinforced with carbon fibers (Torayca (registered trademark) T300 manufactured by Toray Industries, Inc.) oriented spirally around the axis 22 at a pitch angle of ±70°. It shows a cylindrical core made of JIS standard MC8) and having a hollow hole 25 extending along the axis 22. A cylindrical intermediate layer 26 made of stainless steel (JIS standard SUS304) and extending along the axis 22 around the core 21 is provided integrally with the core 21 on the outside of the core 21 . The cylindrical outer peripheral surface of the intermediate layer 26, the surface of the hollow hole 5 of the core 21, and both end surfaces of the core 21 and the intermediate layer 6 are coated with a plating layer 27 of Ni-SiC (nickel in which silicon carbide particles are dispersed). It's covered.

The piston pin constructed as described above was manufactured as follows according to the manufacturing method of the present invention in the same manner as in Example 1 described above.

First, although it is not shown in the figure, carbon fiber (Torayka (registered trademark) T300 manufactured by Toray Industries, Inc., single fiber diameter 7 μm) is placed around a stainless steel (JIS standard SUS304) pipe with an outer diameter of 8 mm and an inner diameter of 6 mm. ) by winding the strand (6000 single yarns) using filament winding, the pitch angle θ=
Cylindrical layers with a pitch angle of 70° and cylindrical layers with a pitch angle θ = -70° are laminated alternately in the radial direction, with an outer diameter of 21 mm and a length.
A 1500 mm cylindrical fiber molded body was formed. After cutting this cylindrical body into a length of 85 mm, the outer diameter is 23 mm and the inner diameter is
21mm long, 105mm long stainless steel (JIS standard
By inserting it into a pipe made of SUS304),
A cylindrical body was formed from a fiber molded body cut to a length of 85 mm and a stainless steel pipe.

Next, after preheating the cylindrical body to 700°C, it is placed in a mold for high-pressure casting, and 690°C molten magnesium alloy (JIS standard MC8) is poured into the mold, and the molten metal is heated to 1500 kg/cm by a plunger. The molten metal was pressurized at a pressure of ² , and the pressurized state was maintained until the molten metal completely solidified. After the molten metal has completely solidified, the solidified body is taken out from the mold using a knock-out pin, and a cylindrical body is taken out by removing the part consisting essentially only of magnesium alloy from the solidified body by machining. The pipe with an outer diameter of 8 mm and the solidified magnesium alloy inside the pipe were removed by massaging with a drill, and the cylindrical outer peripheral surface of the pipe with an outer diameter of 23 mm was ground by about 0.5 mm, and both ends were cut off. As a result, a cylindrical piston pin material having an outer diameter of 21.95 mm, an inner diameter of 8 mm, and a length of 75 mm was obtained. The thus obtained cylindrical body was immersed in a Ni-SiC plating bath, and the surface of the cylindrical body was coated with a Ni-SiC plating layer by electroless plating, as shown in Fig. 9. Outer diameter 22mm, inner diameter 8 as shown
The piston pin was 75 mm in length. The volume fraction of carbon fiber in this piston pin was 65%, and the thickness of the Ni-SiC plating layer was about 30 μm.

The weight of the piston pin manufactured as described above is 79
g, and this piston pin was 34% lighter than a conventional piston pin made of forged steel. In addition, the piston pin manufactured as described above was used for 4 cylinders.
Built into 2000cc gasoline engine, engine speed
When a durability test was conducted for 200 hours at 5200 rpm and full load, it was found that the piston pin described above had sufficient strength and durability. Also, the piston pin mentioned above has all its surfaces
Since it was covered with a Ni-SiC plating layer, galvanic corrosion, which is a problem in composite materials with carbon fiber as reinforcing fiber and magnesium alloy as matrix metal, did not occur.

Although the present invention has been described in detail with reference to two embodiments above, the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is an illustrative perspective view showing a partially cutaway embodiment of a piston pin according to the present invention, FIG. 2 is a partial perspective view showing a fiber molded body, and FIG. 3 is a fiber molded body and stainless steel. Fig. 4 is a cross-sectional view showing the casting process, Fig. 5 is a perspective view showing a piston pin rough material, Fig. 6 is a cross-sectional view showing a compression test mode, Fig. 7 is a graph showing the results of the compression test, and Fig. 8 shows a part of the cross section at 400 times magnification to show the structure of the longitudinal cross section passing through the axis of the piston pin manufactured in Example 1. The optical micrograph, FIG. 9, is an illustrative perspective view, partially cut away, of another embodiment of the piston pin according to the present invention. 1... core, 2... axis, 3... carbon fiber, 4
... Aluminum alloy, 5 ... Hollow hole, 6 ... Intermediate layer, 7 ... Molybdenum coating layer, 8 ... Pipe, 9 ... Fiber molded body, 10 ... Pipe, 11 ...
... Cylindrical body, 12 ... Mold, 13 ... Molten aluminum alloy, 14 ... Plunger, 15 ... Knockout pin, 16 ... Piston pin rough material, 18
... Piston, 18a ... Piston head, 19
... Connecting rod, 20 ... Axis line, 21
... core, 22 ... axis, 23 ... carbon fiber, 2
4... Magnesium alloy, 25... Hollow hole, 26
...Intermediate layer, 27...Ni-SiC plated layer.

Claims (1)

[Scope of Claims] 1. A core portion extending along the axis and made of a light metal composite reinforced with reinforcing fibers spirally oriented around the axis at a pitch angle of ±65° to ±70°; A piston pin comprising a cylindrical intermediate layer made of metal and extending along the axis around the core, and an outer layer of hard metal covering the cylindrical outer peripheral surface of the intermediate layer. 2. Forming a fiber molded body made of reinforcing fibers spirally oriented at a pitch angle of ±65 to ±70° around the axis, and placing the fiber molded body in a metal sleeve,
After preheating this, it is placed in a mold, a molten light metal is poured into the mold, the molten metal is solidified while being pressurized, and a portion consisting essentially only of the light metal is removed from the resulting solidified body. , a method for manufacturing a piston pin in which the cylindrical outer peripheral surface of the metal sleeve is coated with a hard metal.